17 April 2023

The sex of a blood donor has no effect on the risk of mortality of the person who receives red blood cell transfusions, a major clinical trial of more than 8,700 patients in Canada has shown.

The study puts to bed concerns raised in some observational studies that linked female blood donation with a higher risk of death, said joint study leader Dr Dean Fergusson, director of the Ottawa Hospital’s clinical epidemiology program and professor at the University of Ottawa.

The American National Heart, Lung and Blood Institute identified the possible impact of the sex of a blood donor on recipient survival as a research priority in 2015, after some evidence suggested sex-related differences, such as hormone levels in male and female blood, might affect mortality.

Dr Michaël Chassé from Centre Hospitalier de l'Université de Montréal, who led the study jointly with Dr Fergusson, said the innovative double-blind, randomised trial was done inexpensively by embedding the trial in real-world practice and using practical methods.

They enrolled every adult patient at The Ottawa Hospital who might need a transfusion, randomising them to receive male or female blood, and then collected data from existing hospital databases and provincial registries.

As male and female blood were considered equivalent treatments, patients did not need to provide written consent to join the trial but were given the option to opt out after the first transfusion.

The study did not include patients without an Ontario Health Insurance Plan number, those who were bleeding significantly and needed blood immediately, and those with a complex antibody profile that made blood unit matching difficult.

They enrolled 8,719 participants in just over two years, and each was randomly assigned to receive either male or female donor blood at all visits to The Ottawa Hospital during the study period.

Out of the cohort, 80% received their first transfusion while they were an inpatient and 42% of those patients received it during surgery.

The study found no statistically significant differences in overall survival between recipients of male donor blood and recipients of female donor blood. The findings were published in the New England Journal of Medicine.

“Blood is the most common life-saving treatment given in hospital,” said Dr Jason Acker, senior scientist at Canadian Blood Services. “As a blood provider, we were happy to help answer this very important question in transfusion medicine. We hope the findings encourage all eligible donors to continue to donate.”


Chassé M, Fergusson DA, Tinmouth A, Acker JP, Perelman I, Tuttle A, English SW, Hawken S, Forster AJ, Shehata N, Thavorn K, Wilson K, Cober N, Maddison H, Tokessy M. (2023) “The effect of donor sex on recipient mortality in transfusion.” New England Journal of Medicine, doi: 10.1056/NEJMoa2211523

Link: https://www.nejm.org/doi/10.1056/NEJMoa2211523

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